1. Field of the Application
The present application relates to the field of fluid flow in pipes, in particular to the field of anti-siphon valves. More particularly, the present application relates to the field of lubrication of a turbomachine. More particularly, the present application relates to an anti-siphon valve for sucking up a liquid from a tank, in particular an oil tank in the supply circuit of a turbomachine.
2. Description of Related Art
A turbomachine uses oil for different functions. This oil is used primarily to lubricate moving parts, but it can also be used for actuating devices through its pressure. For example, it can be used to adjust the pitch of the fan blades of a turboprop, or to damp movement transferred by the bearings. The oil may also be used to heat or cool certain parts of the turboprop and even the aircraft itself.
To perform these functions, the oil is fed into a supply circuit having a plurality of pumps ensuring its circulation. The circuit generally comprises an oil tank for storing oil, its volume being able to satisfy the engine's oil consumption over a given time, whilst maintaining a safety reserve.
To prevent the tank from emptying by gravity when the turbomachine has stopped, an anti-siphon valve may be located at its output. This anti-siphon valve may be opened by the effect of suction created by a downstream pump. So that the valve opens more reliably, its opening may be assisted by an auxiliary mechanism. This latter is operated by oil discharged by a pump located downstream of the valve.
Published patent FR2654466 A1 discloses a tank of an oil supply circuit of a turbomachine. The tank is fitted with an anti-siphon valve located at the lowest point of the tank. The valve is designed to prevent the oil in the tank being emptied by gravity. The opening of the valve is controlled by an annular chamber surrounding the valve, the chamber being actuated by oil discharged from a pump fitted to the turbomachine's oil supply system.
However, an aircraft turbine engine may be exposed to extreme temperatures, of the order of −40° C. to −50° C. In these circumstances, the oil may solidify in the tank, the valve, the auxiliary mechanism and the control piping.
This solidified oil then risks clogging the piston and slowing its opening. This delay in opening prevents the oil from flowing and creates pressure losses within the valve. It is then necessary to wait some time for the turbomachine to warm up and for its oil once again to become sufficiently fluid to allow actuation of the auxiliary mechanism and the valve to fully open. This warming-up period limits the use of an aircraft turbomachine as stringent safety rules are rigorous in this area. The warming-up period causes operational downtime because of non-use of the turbomachine and/or the corresponding aircraft.
Although great strides have been made in the area of anti-siphon valve, many shortcomings remain.